Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

New type of airplane

  1. Oct 22, 2016 #1

    wolram

    User Avatar
    Gold Member

    This is a supersonic plane with a bi plane layout

    Date:
    March 19, 2012
    Source:
    Massachusetts Institute of Technology
    Summary:
    A researcher has come up with a concept that may solve many of the problems that grounded the Concorde. An assistant professor of aeronautics and astronautics, says the solution, in principle, is simple: Instead of flying with one wing to a side, why not two?

    Do you think it is realistic?
     
  2. jcsd
  3. Oct 22, 2016 #2

    Nidum

    User Avatar
    Science Advisor
    Gold Member

    Probably not but give us specific details and we'll have a look .
     
  4. Oct 22, 2016 #3

    wolram

    User Avatar
    Gold Member

    Sorry here is the link.
     
  5. Oct 22, 2016 #4

    RonL

    User Avatar
    Gold Member

    You having one of my days ? o_O :biggrin:
     
  6. Oct 22, 2016 #5

    wolram

    User Avatar
    Gold Member

  7. Oct 22, 2016 #6

    boneh3ad

    User Avatar
    Science Advisor
    Gold Member

    It doesn't look legit to me. For one, a typical supersonic airplane doesn't even generate its strongest shocks at the wings. That occurs at the nose, and this idea does nothing to address that. Second, I am not sure what they mean by canceling shocks, but that would only happen in the middle of the wings where it won't affect the sonic boom, and even then only at a very narrow Mach number range, so it's only relevant at one flight condition, not the whole envelope. Third, without more information, I have a very difficult time believing this is more efficient than a single, sharp-edge wing at supersonic speeds and an even harder time believing that it is somehow efficient both above and below Mach 1. If it really was, it probably would have been built by now since Busemann originally came up with it in the 1930s.

    I tried looking up the actual paper, but so far I can't find it.

    EDIT: I found the paper. It's all about adjoint methods for optimizing the biplane shape. I am not at work so I can't download the full text right now but it doesn't look like it makes the same conclusions that the article you posted does. It claims it is more efficient than a single airfoil of the same total thickness, which is a no-brainer since for supersonic flows, drag grows substantially with airfoil thickness. It also doesn't appear to mention anything about any of the other sources of drag or shock waves on a plane.
     
    Last edited: Oct 22, 2016
  8. Oct 24, 2016 #7
    One of the main problems with the Concorde was simply the noise. A colleague told me stories about working at La Guardia. He told me that a hangar a mile away from the takeoff of a Concorde would shake and rattle. That had to be so inefficient. I always wondered if anyone in the supersonic industry tried to design a high-bypass engine capable of running at supersonic speeds. That would be quieter and more efficient.

    Gulf stream is working on a supersonic model. Their idea is to extend a boom from the tip of the nose during supersonic flight. The boom shapes the bowshock for better flight control and lower noise.
     
  9. Oct 24, 2016 #8

    boneh3ad

    User Avatar
    Science Advisor
    Gold Member

    The engine design is much less of a problem than wing design. The problem with supersonic transport aircraft is that they must necessarily spend a large portion of time flying at subsonic speeds during takeoff and landing and, given flight rules, any time they are near or over land. Drag on a supersonic wing is governed pretty much entirely on its leading edge shape and thickness. The thinner and sharper it is, the less drag it will experience. On a subsonic wing, it is a more complicated problem, but generally, thin, sharp wings are not only not the most efficient design, but also a very inefficient design. In essence, it means that the Concorde had supersonic wings but had to spend a lot of time at subsonic speeds, and it needed a while lot of thrust during those periods in order to maintain sufficient lift. The fact that it also used turbojets (as opposed to turbofans) compounded the issue.

    At any rate, building a high-bypass turbofan that can go supersonic would be quite diffecult since the drag penalty would be enormous. Supersonic drag is determined in large part by frontal area and how blunt an object is. High-bypass turbofan essentially looks like a very large blunt object flying through the air and its extra drag would almost certainly outweigh its efficiency benefits. That's why you see the engines hidden inside of the structure in many supersonic planes so that they can be hidden behind relatively small, sharp intakes. At the very least, though, you could probably use a low-bypass turbofan that is still small enough to be integrated into the body a little bit better. That would still be an improvement. This is what most modern supersonic business jet concepts do, such as the Aerion AS2 (which, incidentally, also takes steps to try to overcome the wing issue as well).

    The quiet spike that Gulfstream patented is one approach. There are others as well, such as designing the nose tip to help shape the bow shock such that it is more spread out and therefore the boom is weaker. It's an interesting problem.

    I should also note that my above statement in an earlier post about the boom generated by wings being insignificant is not necessarily true. For example, if the wings are not entirely within the shock generated by the nose, then they will be exposed to the full incoming Mach number of the free stream and likely create a stronger shock than the nose cone does. Additionally, depending on the sweep angle of the wing and the strength of the shock from the nose, the wings may still contribute significantly to the boom.

    Also, it should be noted that the Busemann biplane, about which the original article posted by @wolram was written, only results in no shocks projected away from the wing when it is at zero angle of attack. It also turns out that it produces zero lift in this configuration. In that configuration, it does indeed have very low drag and no outward-projected shock waves. However, if you wanted to actually use it to provide lift to a plane, then it will still generate a shock that would likely be experienced on the ground.
     
  10. Oct 24, 2016 #9
    Angry communities could torpedo a billion dollar project if it's too loud. Sorry, I forgot to actually make that point. Noise is high on the priority list in the aerospace industry. It's risky to invest big bucks into a design if airports will not receive your aircraft. The bright side of this is that noise reduction brings energy efficiency with it.

    It's just a musing of mine. I agree it would be a challenge, maybe impossible.
     
  11. Oct 24, 2016 #10

    boneh3ad

    User Avatar
    Science Advisor
    Gold Member

    Sure, noise is a big issue, but with a supersonic plane, the sonic boom is much louder than the engine, and at any rate, the engine noise is going to be mitigated quite a bit by using a newer design. For any given engine, the noise it puts out is largely driven by how much power is currently required from it, which must be much higher over populated areas when you are required to use a supersonic wing for subsonic flight. If you mitigate the boom such that the plan can fly supersonically over populated areas, then you likely have less engine noise as well, so you kill two birds with one stone there.
     
  12. Oct 24, 2016 #11
    That's an excellent point I hadn't thought of that.

    The issue I see coming up is how loud the engines would be at takeoff power. Major airports have a kind of budget for noise levels which they cannot go above. I think we would agree that a supersonic capable engine will tend to be loud at max power. That's an educated guess on my part. This isn't my field but I notice that high speed military engines don't have the diffuser kits which mitigate noise.

    Is there a new design? I really think the engine might be big hangup for a new supersonic transport.

    I was kinda curious how it would work if we were going to pursue this design in the US. If you want to make this a large transport aircraft eligible for commuter service routes then you would need to a type certificate issued by the FAA. 14 CFR part 36 governs noise levels for airworthiness certificates. I saw something interesting in that chapter. There is one exception made in the regulations for the Concorde. Somebody successfully lobbied the FAA for a noise exception. It could be done again.

    The only other way I see this working would be to build it in a nation that has an aviation treaty with the US and lax noise rules. The FAA honors the regulations of its allies. That doesn't mean that airports have to accept the aircraft. We would probably need to get some major hubs on board.
     
  13. Oct 24, 2016 #12

    boneh3ad

    User Avatar
    Science Advisor
    Gold Member

    I believe that is correct. I am not an engine expert, but generally speaking, the lower bypass you have, the louder it will be for a given engine core, and since a supersonic engine will necessarily have a lower bypass, it will tend to be louder, all else being equal.

    Sure there is. A modern jet fighter, for example, uses a turbofan (albeit with a very low bypass ratio, e.g. something like 0.3:1 on the F-22). The Concorde used straight up turbojet engines (i.e. bypass ratio of zero). Of course, a modern high-bypass turbofan has a bypass ratio closer to 10:1, but even something small like 0.3:1 will have noise and efficiency improvements over a turbojet and will remain compact enough to tuck into the fuselage.

    While I am not personally involved in any of the modern supersonic transport programs, my understanding is that the sonic boom issue is a much greater problem than the noise generated at takeoff and landing by the engines. If using such a craft is to be cost effective, it really needs to be able to go supersonic closer to shore, and even better if it is over land since then it can be used for continental flights. Perhaps the jet noise issue has just been downplayed because most modern concepts are business jets, so they will be quieter on account of their size and scaling up to a 737-type size would still be problematic. That I can't answer. I do know that most of these designs have mostly assumed that they could build the demonstrators and then prove to regulators that their booms are small enough (or nonexistent enough) that they can still fly over land. It sure would be neat if it works out that way.
     
  14. Oct 26, 2016 #13
    Whenever a new supersonic transport concept comes out, I can't help but wonder if there is really a market for such an aircraft. Of course it's fun to read about the latest tech and imagine what it would be like to travel on an SST, but it would never come to fruition if it wasn't more profitable than what already exists. It doesn't seem likely that airlines would jump at the chance to buy a fleet of airplanes with high maintenance demands and high operating costs so that they could sell expensive tickets to save passengers a few hours of time. I'm not familiar with the economics of how airlines operate by any means, it just sounds kinda unlikely that an SST would be a good investment for a carrier unless it had incredibly low operating costs for its performance. Modern subsonic airliners with high-bypass turbofans are efficient enough that I would be surprised if an SST could compensate for its higher operating costs with shorter flight times.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: New type of airplane
  1. WW2 airplane submarine (Replies: 5)

  2. Two Types of valves (Replies: 1)

  3. Types of counterweights (Replies: 12)

Loading...